code: def __len__(self):
      return len(self.loader)
  
imports: import torch
  import shutil
  import dill
  import os
  from subprocess import Popen, PIPE
  import pandas
  from PIL import Image
  from .None import constants
label_desc: Use image node_id 2 for calling the DataPrefetcher obj's underlying member method code with example usage: obj.__len__() and returns: len